1. Field of the Invention
The invention relates generally to tubular pipe fittings and more particularly to a pipe elbow construction which provides a high resistance to abrasive wear when carrying abrasive fluids.
2. Description of the Prior Art
Before coal can be burned in power generating boilers, it must first be pulverized and then pneumatically moved from the pulverizer to the combustion chamber of a boiler. The coal requirements in modern generating units are enormous and often exceed 500 tons per hour for a single boiler. The need to move such large volumes of a highly abrasive material places great demands on the piping system through which it is conveyed. As one might expect, excessive wear is a common occurrence throughout the system with the problem being especially severe in the pipe elbows which change the direction of flow.
As is known, upon a change in the direction of flow of a fluent containing abrasive particles, the wall facing the oncoming stream is subjected to a continuous bombardment of such particles. The result is that the outer bends of the pipe elbows in these coal transport systems are rapidly worn down and the fittings must be patched or replaced at frequent intervals. The down time and other costs accrued in the need to continually make such repairs represents a substantial economic loss.
In previous attempts to resolve this problem, a variety of approaches have been taken but a wholly satisfactory solution has not resulted from these efforts.
As illustrated in U.S. Pat. Nos. 1,246,189 and 3,551,006, one approach has been to provide the elbow with an abrasion-resistant lining.
In U.S. Pat. No. 1,211,784, an elbow construction is described which consists of two separate semicylindrical sections with the medial portion of one section being enlarged to accommodate a recess into which lining blocks are inserted.
Another approach is illustrated in U.S. Pat. No. 3,977,730 where an impact plate is fixed to the outside surface of the outer bend of the elbow.
In U.S. Pat. No. 3,794,359 a pipe elbow fabricated entirely from non-metallic materials is described. The elbow consists of a pair of wear plates of ceramic material having a semi-circular shape and assembled circumferentially in opposing spaced relationship to each other. A resinous grout is disposed in the circumferential space between the opposed wear plates and a fiberglass reinforced resin provides a cover over the wear plates and grout.
With the foregoing in mind, the object of the present invention is to provide a wear resistant elbow fitting which offers advantages not heretofore afforded by any known prior art constructions.